1. Field of the Invention
The present invention relates to a setting tool for driving fastening elements such as, e.g., bolts, nails, pins in a constructional component and including a combustion chamber for an oxidant-fuel gas mixture, a guide cylinder adjoining the combustion chamber at one of its ends, a setting piston displaceable in the guide cylinder for driving a fastening element in the workpiece, a plate-shaped member axially displaceable in the combustion chamber for creating turbulence therein, means for displacing the plate-shaped member, and a holding device for retaining the plate-shaped member at an axial end of the combustion chamber against action of the displacing means.
2. Description of the Prior Art
Setting tools of the type described above are driven with gaseous fuels or liquid fuels which are evaporated before combustion. The setting energy for driving in a fastening element is obtained by combustion of an oxidant-fuel mixture in a combustion chamber and is transmitted to the to-be-driven-in fastening element by a setting piston. As an oxidant, e.g., oxygen from the environmental air is used. For optimal energy efficiency, it is desirable that the combustion of the oxidant-fuel mixture takes place in a turbulent flow regime.
U.S. Pat. No. 6,892,524 discloses a combustion-engined setting tool having a combustion chamber for combusting an oxidant-fuel mixture, a guide cylinder, and a setting piston displaceable in the guide cylinder and driven by a working pressure produced by combustion of the oxidant-fuel mixture. In the combustion chamber of the setting tool, there is arranged a separation plate provided with holes and which is displaceable along a longitudinal axis of the combustion chamber with another plate. The combustion chamber further has a combustion chamber rear wall displaceable relative to the separation and another plates.
After the setting tool was pressed against a constructional component, the separation plate and another plate are located at an axial end of the combustion chamber remote from the setting piston. The separation plate is retained on another plate against a spring biasing force by a latch mechanism. The latch mechanism is actuated by the tool actuation switch, and in response to the actuation of the switch, the separation plate is lifted off another plate by a spring and is displaced a certain amount in the combustion chamber, dividing the combustion chamber in two sub-chambers.
The two sub-chambers are connected with each other by openings provided in the separation plate.
The drawback of the setting tool described above consists in that the latch mechanism consists of a large number of parts interacting with each other, generating frictional forces. The parts are also subjected to soiling and require narrow tolerances. All this can lead to high actuation forces or even to the failure of the latch mechanism
Accordingly, an object of the present invention is a setting tool of a type described above in which the drawbacks of the known setting tool are eliminated.